Japanese Unexamined Patent Application Publication No. 2008-292523 describes an optical fiber fusion splicer that includes a pair of grasping structures, which each grasp an optical fiber, and a pair of arc electrodes, which are disposed between the grasping structures. Each grasping structure of the optical fiber fusion splicer includes a V-shaped groove base, which has a V-shaped groove that receives a bare fiber located in a distal end portion of the optical fiber, and a fiber clamp, which clamps the bare fiber received by the V-shaped groove. However, in this optical fiber fusion splicer, when the fiber clamps are to clamp bare fibers, the bare fibers are sometimes disposed obliquely with respect to the V-shaped grooves (fiber grooves) due to warping of the optical fibers and thus the bare fibers are clamped without being received by the fiber grooves.